Photochromic Lens

ABSTRACT

A cast photochromic lens including a photochromic film and a cast resin, curable by heat or radiation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/741,290 filed Jan. 14, 2013, entitled Photochromic Lens which is adivisional of U.S. patent application Ser. No. 12/959,201 filed Dec. 2,2010 entitled Photochromic Lens (now U.S. Pat. No. 8,367,211 issued Feb.5, 2013); which is a divisional of U.S. patent application Ser. No.11/537,571 filed Sep. 29, 2006 entitled Photochromic Lens (now U.S. Pat.No. 7,858,001 issued Dec. 28, 2010); which claims the benefit ofpriority from U.S. Provisional Application Ser. No. 60/722,848 filed onSep. 29, 2005 entitled Photochromic Lens, and which is aContinuation-In-Part of U.S. application Ser. No. 10/938,275 filed onSep. 9, 2004 entitled Photochromic Polyurethane Laminate (now U.S. Pat.No. 8,298,671 issued Oct. 30, 2012); which claims the benefit ofpriority from U.S. Provisional Application Ser. No. 60/501,819 filedSep. 9, 2003 entitled Photochromic Film and Method of Manufacture, andfrom U.S. Provisional Application Ser. No. 60/501,820 filed on Sep. 9,2003 entitled Photochromic Laminate; all of which are herebyincorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

Many methods and devices are known in the art for incorporatingphotochromic characteristics into an ophthalmic lens. One example of amethod known in the art includes imbibing or infusing photochromes intothe host material or base lens from a transfer layer (that issubsequently removed) prior to formation of the finished lens product.Another example of a method known in the art includes incorporatingphotochromes into a lens by imbibing or coating a photochromiccomposition onto the surface of a base lens. Yet another example of amethod known in the art includes incorporating photochromes into afinished lens product by combining a prepared photochromic insert or“laminate” with base lens material, typically via an injection moldingprocess. The following are illustrative examples of such methods knownin the art.

The imbibing process was one of the first processes to be used to impartphotochromicity to plastic lenses. U.S. Pat. No. 4,286,957 to Naour-Senedescribes this process. Further refinements were discussed in U.S. Pat.No. 4,880,667 to Welch. Various improvements to this imbibing processhave been developed, such as described in U.S. Pat. No. 5,130,353 toFisher et al., and U.S. Pat. No. 5,185,390 to Fisher et al. These twopatents suggest improvements to the transfer process with a uniquetransfer layer. It was recognized early on that the plastic resins usedto make ophthalmic lenses do not provide the best host material forphotochromes. In such plastic resin materials, the photochromes do notactivate easily and fatigue or wear-out in a short period of time. Astrong activation darkness to near sunglass darkness is desired in themarketplace. Another desired characteristic of a photochromic lens isthat it should maintain at least 70 percent of its original activationdarkness after two years of wear. This is one of the limitations toputting photochromes into polymeric host materials that are used to formthe bulk of the lens.

A more recent example, U.S. Pat. No. 5,728,758 to Smith describes aphotochromic article in which the organic polymeric host material hasbeen impregnated with photochromes prior to formation of the finishedlens product. As is described in the '758 patent, one of the drawbacksof incorporating photochromes directly into the polymeric host materialis the problem of fatigue or light fatigue. Photochromes are believed tolose their ability to change color specifically resulting from theirreversible decomposition of the photochromic compound, which occursdue to repeated exposure to UV light over time. The '758 patentspecifically address this problem by using a unique combination ofmonomers and surface coating compositions to improve abrasionresistance, chemical attack and improved fatigue resistance.

Alternatively, an example that describes coating of a photochromic layeronto the surface of a lens is found in U.S. Pat. No. 4,756,973 toSakagami et al. The '973 patent specifically describes the use ofspirooxazine compound and phenolic compound in the photochromic layer,and describes that such a lens formulation provides successful coloringeffects in photochromic lenses that are subjected to environmentalconditions ranging from normal to high temperatures.

Another example that describes coating photochromes on the surface of alens substrate is found in U.S. Pat. No. 6,150,430 to Walters et al.Specifically, the '430 patent describes a process that includes thesteps of treating the surface of a polymeric substrate to providereactive groups, applying a polymerizable composition to the surface,exposing the coated substrate to radiation to improve adhesion, andapplying and curing a photochromic composition to the coated surface.The '430 patent, at least in part, addresses a method of producingcommercially acceptable “cosmetic” standards for photochromic andnon-photochromic optical coatings that are applied to lenses. A majorlimitation of the photochromic coating approach is the poor scratchresistance of such a coating even with another hard coating on top ofthe photochromic coating. Additionally, if the photochromic coating isscratched, it will result in streaks of areas on the lens that do notactivate.

The limitations of the performance of the photochromes in the variousplastics used to make ophthalmic lenses have resulted in variousimprovement methods, including making composite or multiple part lensesthat combine plastics that are good photochromic hosts with additionalplastics to make improved ophthalmic lenses. One example of thisapproach is described in U.S. Pat. No. 5,531,940 to Gupta et al. Anotherapproach is to put the photochromic dyes in the glue layer between twolens sections as described in U.S. Pat. No. 5,851,328 to Kohan. Morerecent attempts at making photochromic composites are described in U.S.Pat. Nos. 6,863,844 and 6,863,848 to Engardio et al. and U.S.Publication No. 20050089630 to Schlunt et al. One problem with theseapproaches is that the mechanical stability of the composite is not verydurable in subsequent processing to make the ophthalmic lens and mountit into a frame. Processes such as surfacing the lens to prescriptionpower and edge cutting to fit into a frame result in chipping of thecomposite due to the different cutting and grinding characteristics ofthe materials. Drilling of the composite to mount into rimless framesalso results in chipping of the composite.

Lastly, the following methods known in the art illustrate incorporationof photochromes into ophthalmic lenses via photochromic inserts orlaminates, whether by cast-mold-type processes or by injection moldingprocesses. For example, U.S. Pat. No. 4,889,413 to Ormsby et al.describes creation of a finished laminate product that is created byplacing two glass or plastic layers into a mold and injecting aphotochromically-infused plastic resin between the glass/plastic layers.The resulting photochromic laminate is thereafter cured and processed,producing a finished lens product.

Another example that illustrates the use of a photochromic insert orlaminate in an injection molding process is described in U.S. Pat. No.6,328,446 to Bhalakia et al. The photochromic laminate or wafer includesinner and outer resin sheets (or protective layers), which sandwich aphotochromic cellulose acetate butyrate layer. The unitary photochromiclaminate is thereafter placed inside a mold cavity, after which a moltenpolycarbonate resin is injected into the cavity and fused to the back ofthe photochromic laminate. The lens is then cooled to room temperatureand the finished product is an injection molded, photochromicpolycarbonate lens.

While each of the above-referenced patents and published applicationsdescribe methods of making photochromic lenses and address particularproblems in the art, improvements are still required. For example,problems associated with impregnating photochromes within the hostmaterial of a base lens have been described to some degree above.Additionally, if such a lens is a semi-finished product and requiresfurther processing (e.g., grinding, polishing, etc), it is clear thatphotochromes present in the base lens will be ground and/or polishedaway, inevitably diminishing the desired coloring effects of thefinished lens product. In addition, the prescription lens must be robustenough to maintain its integrity through subsequent processing both toform the prescription and to be edged, cut and possibly drilled formounting into a frame.

Alternatively, the shortcomings of coating photochromic products ontothe surface of a lens have to do primarily with coating thickness andthe creation of segmented, multi-focal lenses. For example, a coating ofabout 25 μm or more is needed to incorporate a sufficient amount ofphotochromic compounds to provide the desired light blocking quality inthe lens when the compounds are activated. However, a coating of thisthickness is not well suited for application on the surface of asegmented, multi-focal lens because it is too thick. Typically, acoating of this thickness creates such problems as the creation of anunacceptable segment line, as well as coating thickness uniformityissues around the segment line.

Problems that have been raised particularly regarding use ofphotochromic laminates or inserts in injection molding process include,primarily, the bleeding of the functional layer (e.g., photochromiclayer) material of the laminate or wafer. By the term “bleeding,” it ismeant that the functional layer materials between the transparent resinsheets (e.g., the protective layer of the laminate or wafer) runs outfrom between the resin sheets in the lateral direction.

Often bleeding occurs due to the deformation of the photochromic layerunder the high temperature and pressure used during the injectionmolding process. This is thought to occur due to either an excess amountof functional layer material and/or inadequate softening properties ofthe functional layer material. Further, this bleeding can interfere withany additional coating layers that are applied to the lens afterinjection-molding. The Bhalakia patent adequately addresses the issue ofmaking laminates used in injection-molding, through improvement oflaminate materials and properties. However, the issues addressed byBhalakia do not include providing a laminate or insert that may be usedin a cast-lens manufacturing process.

Therefore, a need exists to create a photochromic lens that addressesthe problem of maximizing photochromic properties of a lens produced ina cast-mold manufacturing process.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a photochromic lensthat includes a relatively long service life and provides goodresistance to photochromic dye fatigue. It is another object of thepresent invention to provide a photochromic lens that reduces the amountof photochromic dyes used during the manufacturing process. It is yetanother embodiment of the present invention to provide a photochromiclens that is not limited from use with surface designs, such as bi-focallenses.

It is yet another object of the present invention to provide a method ofmanufacturing a photochromic lens that can utilize most commerciallyavailable cast resins, such as those made by thermoset or radiationinitiated processes. It is yet another embodiment of the presentinvention to provide a photochromic lens having high impact resistance,using known and commercially available high impact resinous layers andmaterials, such as polycarbonate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a photochromic lens according to a preferredembodiment of the present invention.

FIGS. 2A-2D illustrate a photochromic film, as embedded in aphotochromic lens of FIG. 1), according to a preferred embodiment of thepresent invention.

FIG. 3 illustrates a photochromic lens according to a preferredembodiment of the present invention.

FIG. 4 illustrates a cross-sectional view of a cast lens mold known inthe art.

DETAILED DESCRIPTION OF THE INVENTION

As seen in FIG. 1, one embodiment according to the present inventionrelates to a photochromic lens comprising a front cast resin layer 1, aphotochromic film 2, and a back cast resin layer 3. Specifically, apreferred embodiment would include a photochromic lens made from a castresin that is either thermoset or radiation-set. The photochromic lensmay be either a finished product or a semi-finished product. In oneembodiment (as shown in FIG. 2), a photochromic lens may include aphotochromic film 2 including at least one protective layer 4 and aphotochromic layer 5 (as shown in FIG. 2, examples (A),(B) and (C)). Inanother embodiment, the photochromic film may include just aphotochromic layer 5 (as shown in FIG. 2, example (D)). In each of theseembodiments, the photochromic film 2 is bonded or adhered strongly to acasting resin layer 1, 3 during a casting process (as shown in FIG. 1).The photochromic film 2 in the form of a laminate may be optimized as ahost for a photochromic dye to provide for maximum performance of thedye.

As seen in FIG. 2, additional embodiments according to the presentinvention would include a photochromic film 2 having at least oneprotective layer 4 and a photochromic layer 5, in a variety oforientations to one another (e.g., FIG. 2, examples (A), (B), and (C)).As shown in FIG. 3, hard coating, primer, or barrier coatings may beapplied onto the front surface of the protective layer 4 (e.g., forenhancing adhesion and other performances), the front surface meaningthe surface of the protective layer 4 of film 2 laminate facing awayfrom the photochromic layer 5. When the photochromic layer 5 is used asa photochromic film 2 without protective layers 4, the photochromiclayer 5 may also have such hard, primer or barrier coatings appliedbefore placement into the cast lens.

Additional embodiments according to the present invention may include acast photochromic lens including a number of layers and/or combinationsof layers, comprising, for example, protective layers, photochromiclayers or films, and/or additional coating layers (e.g. hard coating,primer layers, and/or other barrier layers) (not shown). Each of theabove-described photochromic lenses can be conveniently manufacturedthrough a casting process.

A suitable photochromic film (laminate) is disclosed in U.S. patentapplication Ser. No. 10/938,275 entitled Photochromic PolyurethaneLaminate, filed Sep. 9, 2004, which is herein incorporated by reference.A preferred material for the protective layers 4 of the photochromicfilm 2 should have good compatibility with the lens casting material. Bythe term “compatibility”, it is meant that the adhesion between theprotective layer 4 and the front cast resin layer 1 formed by the lenscasting material is sufficient to pass ordinary tests for eyewear lenseswithout damage or chemical attack to the protective layers 4 of thephotochromic film 2 (e.g. FDA drop-ball test, drilling and mountingtests).

Examples of preferred materials for the protective layers 4 of thephotochromic film 2 include acrylate resins, cellulose esters, andpolycarbonate resins. Suitable hard coatings known in the art mayfurther protect such protective layer resins to prevent the castingresin from chemically attacking the protective layer resins duringprocessing.

Preferred materials for the photochromic layer 5 of the presentinvention would include, for example, plastic host resins having a glasstransition temperature, T_(g), of less than 50 degrees Celsius, and morepreferably, below 30 degrees Celsius. These plastics tend to bemechanically soft which is ideal for the photochromes to activate andde-activate. When the photochromic dyes absorb UV light, typically acarbon-oxygen bond in the photochromic dye molecule is broken and thedye molecule rotates into a form that absorbs visible light. A softplastic host for the dye that would facilitate this action preferablywould include a class of plastic hosts, such as polyurethanes. However,historically, this mechanical softness of plastic hosts has been showndeficient when such materials are used as ophthalmic lens materials.Therefore, a preferred embodiment of an ophthalmic lens contemplated foruse with the present invention would include encapsulation of a hosturethane resin, such as a photochromic layer 5, within an ophthalmiclens. A preferred thickness of the photochromic layer 5, namely thephotochromic urethane layer 5, would preferably be 10 mil or less, morepreferably 4 mil or less and most preferably, to 2 mil or less.

Preferred polyurethane photochromic host materials would include, forexample, thermoplastic and thermoset polyurethanes. Examples of suchhost materials are disclosed in U.S. Pat. Nos. 4,889,413, 6,107,395, and6,166,129, and U.S. patent application Ser. No. 10/938,275, which areherein incorporated by reference. The polyurethane composition wouldpreferably include the following: 0.05% to 6% pbw of photochromiccompound(s), and a stabilizer package: 0.5% to 6% pbw of lightstabilizer(s), 0.5% to 6% pbw of antioxidant(s), 0.5% to 6% pbw of UVabsorber(s). Also, the photochromic film 2 would preferably have athickness no greater than 40 mil.

Any lens casting resins available on the market and known in the artwould be suitable to produce the photochromic lens of the presentinvention. Examples of such casting resins would include the opticalmonomer CR-39, allyl diglycol carbonate, from PPG (or equivalent fromGreat Lakes Chemicals denoted by the tradename of RAV-7) and the opticalmonomer MR series cast resins from Mitsui. In addition to thermosetresins, cast resins that are curable by radiation energy (e.g., UV) arealso suitable for use with the present invention. The radiation curingprocess is advantageous in that it will not interfere or degrade thephotochromic dyes due to their protection inside the laminate. Examplesof radiation curable cast resins would include, for example, thoseresins based on acrylate chemistry.

It is preferable that the cast resin for the front protective layer 4 ofthe photochromic film 2 should not include UV absorbers, which wouldsignificantly absorb or block the activation wavelength of thephotochromic dye. The photochromic layer 5 of the photochromic film 2would provide adequate UV protection to the eyes, as the photochromicdyes imparted to the photochromic layer 5 are extremely efficientabsorbers of UV.

Examples of manufacturing the photochromic lens as contemplated in thepresent invention would include, for instance, a cast molding process,in which a photochromic film 2 is first placed into a cast mold 8, shownin FIG. 4. Thereafter, a cast resin 1,3 may also be introduced into thecast mold 8 and the lens would be cured, forming an integratephotochromic cast lens. The photochromic film 2 may be placed in anynumber of orientations within the mold, depending upon desired resultsand lens processing applications.

One embodiment for manufacturing the lens of the present invention wouldinclude the steps of preparing a photochromic film 2, as earlierdescribed; forming discs of the film into wafers, preferably having acurve matching the front base curve of the lens to be produced;preparing a cast setup comprising a front mold 34, a formed wafer orfilm 2, a back lid (mold) 32, in a cast gasket; pouring a cast resininto the front cavity 70 formed by the front mold and the wafer 2, andthe back cavity 72 formed by the wafer 2 and the back lid (mold) 32; andcuring the cast resin to form the photochromic lens.

Forming of the photochromic film 2 may be done by a variety of differentways familiar to those in the arts. Examples of lens forming techniquesmay include, for instance, compression forming and vacuum forming.

A cast setup used to produce polarizing lenses from cast resins couldalso used to cast the photochromic lens of the present invention withoutany modification.

Another embodiment for manufacturing a lens as contemplated by thepresent invention includes incorporation of photochromes into thepolyurethane plastic, and thus the photochromic film 2, after thepolyurethane has been formed (e.g., after urethane monomers and catalysthave reacted to fully form polyurethane). This is contrary to theteaching of U.S. Pat. No. 4,889,413 (herein incorporated by reference),which describes incorporation of photochromes into the urethanemonomer/catalyst mixture, prior to formation of polyurethane. Further,the teaching of the '413 patent describes a method of preparing andassembling a lens unlike that of the present invention. The '413 patentdescribes assembly of pre-cast lenses (either plastic or glass), betweenwhich a photochromic host is introduced and thereafter cured.

One embodiment of a method contemplated for use with the presentinvention may include the steps of: dissolving an appropriate amount ofphotochromic dye into a polyurethane resin with an appropriate solvent;casting the resultant solution on a smooth surface, to allow the solventto evaporate; placing the resulting sheet or film of photochromicpolyurethane into a mold with a thermoset casting monomer liquid andcatalyst; and completing a curing or reaction step of the thermosetmonomer into a thermoset, fully cured lens with the polyurethane filmencased inside the thermoset lens.

This particular embodiment would result in a photochromic thermoset,cast lens with improved photochromic properties. Thus, one does not needto mix the photochromes with the polyurethane monomers first. One hasthe option of putting the polyurethane in a laminate as described aboveor not in a laminate inside the lens (plastic host).

Example 1

A photochromic film was prepared according to the examples in U.S.patent application Ser. No. 10/938,275. The polyurethane layer is 40 μmthick, and the protective layers are 76 μm cellulose acetate butyrate(CAB) films (K-Mac). The polyurethane layer and protective layers werebonded together to form a photochromic laminate. The laminate was maskedwith a polypropylene 3M film (24S56W). A 70-mm disk was die-cut off fromthe above laminate, and formed into a 6-base laminate wafer through athermo-vacuum forming process. The temperature was 255° F., and theforming time was 200 seconds. A 70-mm lens cast gasket and two 6-baseglass molds (front and back) were used to cast the photochromic lens.The masked film is thereafter removed prior to placement of the laminatewafer into the gasket. The laminate wafer was fixed in the gasket about1 mm away from the front mold surface with help of a spacer. A clearUV-curable cast resin from OptiCast was injected into the front and backcavities. The front cavity is formed by the front mold and thephotochromic film. The cast resin in the above setup was cured under a12-mW/m² exposure for 10 minutes. The result was a cast resin lenshaving the photochromic film embedded in it. The unactivatedtransmission of the lens was measured as 70%. The activated transmissionafter exposure to a Xenon lamp under 20 W/m² intensity of UV wasmeasured to be 19%. This demonstrated good photochromic activity.

Example 2

To a solution of 18% by weight of a polyester urethane (Tecoflex CLC-93Afrom Thermedics) in THF solvent was added 2% each of Tinuvins 765(Mixture of Bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and methyl1,2,2,6,6-pentamethyl-4-piperidyl sebecate), 144(Bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmaloate), and Irganox 1010 (Pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) (all fromCIBA Corporation), and 0.8% of naphthopyran photochromic dye VP0762(Proprietary Vision-Ease Dye). The mixture was then cast on a flatborosilicate glass plate and the solvent allowed to evaporate. Aphotochromic film of about 0.2 mm thick was obtained. The photochromicfilm was then placed between two glass molds held together with astandard casting gasket. A mixture of 58.3 grams of casting monomer P11(NOF Corporation), 0.6 gram of Tinuvin 765, 0.26 gram of Trigonox 7(tert-Butyl peroxydiethylacet) catalyst and 0.37 gram of Trigonox 21(tert-Butyl peroxy-2-ethylhexanoat) catalyst was introduced between theglass molds and around the polyurethane film. The mold and gasketassembly was placed in a water bath and cured in a cycle that ramps thelens up to 90 degrees Celsius over a 20 hour period. The resultantthermoset, cast lens is then separated from the glass molds. The lenshad a refractive index of 1.55. The lens sample was then fatigued byexposure to a Xenon lamp with an ultraviolet light output of 30Watts/Square Meter for 144 hours. This simulates actual wear of the lensby someone for a two year wear period. After the 144 hours, thephotochromic performance remaining was 97%. This compares to theperformance of the commercial photochromic polycarbonate Quantum(Transitions Optical, Inc.) lens product that is believed to be only a65% remaining performance. Thus, the photochromic film in the cast lenswas very fatigue resistant and had longer life than the prior art.

Example 3

A photochromic film was prepared according to the examples in U.S.patent application Ser. No. 10/938,275 (now U.S. Pat. No. 8,298,671issued Oct. 30, 2012). The polyurethane layer is 40 μm thick, and theprotective layers are 350 μm thick polycarbonate films. The polyurethanelayer and protective layers were bonded together to form a photochromiclaminate. The laminate was masked with a 3M film (24S56W). A 70-mm diskwas die-cut off from the above laminate, and formed into a 6-baselaminate wafer through a thermo-vacuum forming process. The temperaturewas 255 degrees Fahrenheit, and the forming time was 200 seconds. A70-mm lens cast gasket and two 6-base glass molds (front and back) wereused to cast the photochromic lens. The masked film is thereafterremoved prior to placement of the laminate wafer into the gasket. Thelaminate wafer was placed against the front mold surface and placed intothe gasket with the back mold. A clear UV-curable cast resin fromOptiCast (OPIV-B) was injected into the back cavity. The cast resin inthe above setup was cured under a 12-mW/m² UV exposure for 7 minutes.The result was a cast resin lens having the photochromic laminate fusedto the front of it. The unactivated transmission of the lens wasmeasured as 79%. The activated transmission after exposure to a Xenonlamp under 12 W/m² intensity of UV was measured to be 19%. Thisdemonstrated good photochromic activity.

Example 4

A photochromic film was prepared by laminating 13.5 mil thick CAB film(Kodacel K7896, made by Eastman Kodak) for both top and bottomprotective layers and 38 micron photochromic layer (polyurethane). Thelaminate was masked with 3M protective masking film (24S56W) on bothsides, then a 86 mm disk in diameter was cut-out from the abovelaminate. It was formed into a 6 base laminate wafer through athermo-vacuum forming process. The forming temperature was 75 degreesFahrenheit and forming time was 150 seconds. It was further cut to 72.6mm in diameter to fit the size of casting mold. It was further cut by 3mm on two locations to allow flow of the cast resin around it. A 73 mmcasting mold and two 6 base glass molds were used for front and back tocast a photochromic lens. The masked film is thereafter removed prior toplacement of the laminate wafer into the gasket. Said formedphotochromic film was placed in the mold about 1 mm away from the frontmold surface with help of a spacer. Thermo-set resin RAV-7 (made byGreat Lakes Chemical) without UV absorbing agent was injected to fillboth front cavity and back cavity which were separated by thephotochromic film. The cast resin in the above setup was thermally curedin normal condition. The result was a cast resin lens having thephotochromic laminate fused to the front of it. The unactivatedtransmission of the lens was measured as 82.4%. The activatedtransmission after exposure to a Xenon lamp under 12 W/m2 intensity ofUV was measured to be 16%. This demonstrated good photochromic activity.

Example 5

A photochromic film was prepared by laminating 12 mil thickpolycarbonate film (1151 by Teijin Kasei America) for both top andbottom protective layers and 38 micron photochromic layer(polyurethane). The polycarbonate film was applied with UV curablehardcoat as barrier coating on one side in advance. The hardcoated sidewas placed outside of lamination that later contacts casting resin.Without this barrier coating, this casting resin monomer has been shownto cause the polycarbonate film to turn white and, therefore, unusable.The laminate was masked with 3M protective masking film (24S56W) on bothsides, then a 86 mm disk in diameter was cut-out from the abovelaminate. It was formed into a 6 base laminate wafer through athermo-vacuum forming process. The forming temperature was 285 degreesFahrenheit and forming time was 250 seconds. It was further cut to 72.6mm in diameter to fit the size of casting mold. It was further cut by 3mm on two locations to allow flow of the cast resin around it. A 73 mmcasting mold and two 6 base glass molds were used for front and back tocast a photochromic lens. The masked film is thereafter removed prior toplacement of the laminate wafer into the gasket. Said formedphotochromic film was placed in the mold about 1 mm away from the frontmold surface with help of a spacer. Thermo-set resin RAV-7 (made byGreat Lakes Chemical) without UV absorbing agent was injected to fillboth front cavity and back cavity which were separated by thephotochromic film. The cast resin in the above setup was thermally curedin normal condition. The result was a cast resin lens having thephotochromic laminate fused to the front of it. The unactivatedtransmission of the lens was measured as 90.0%. The activatedtransmission after exposure to a Xenon lamp under 12 W/m2 intensity ofUV was measured to be 19%. This demonstrated good photochromic activity.

In yet another embodiment, the present invention provides a photochromicpolyurethane laminate having two transparent resin sheets bonded to aphotochromic polyurethane layer formed by curing a mixture of a solidthermoplastic polyurethane, at least one isocyanate prepolymer, at leastone photochromic compound, and a stabilizing system. The thermoplasticpolyurethane has a theoretical NCO index of from 90 to 105, and amolecular weight (number averaged) of from 20,000 to 100,000. Theisocyanate prepolymer has a NCO content of from 1.0% to 10.0%, byweight. The weight ratio of the thermoplastic polyurethane vs. theisocyanate prepolymer in the photochromic polyurethane composition is inthe range from 1:9 to 9:1. The photochromic compound(s) counts for 0.1%to 5% of the total polyurethane, by weight.

To enhance the fatigue resistance of the photochromic compounds,stabilizers such as antioxidants, light stabilizers, and UV absorbersare added in the polyurethane layer.

The photochromic laminate is preferably made through a cast-laminationprocess. All components described above are dissolved in a suitablesolvent, cast on a release liner. After the solvent is evaporatedsubstantially, the thermoplastic polyurethane portion will provide thecast polyurethane film enough rigidity to go through the laminationprocess without any deformation. After lamination, the polyurethaneprepolymer will provide further curability by reacting with activehydrogen atoms such as those of terminal hydroxyl groups, moisture,urethane groups, and urea groups in the system to enhance thedimensional stability of the polyurethane layer under high temperatureand high pressure.

Transparent Resin Sheets

The material used to make the transparent resin sheet is not limited solong as it is a resin with high transparency. In case the photochromicpolyurethane laminate of the present invention is incorporated into athermoplastic article such as a spectacle lens, the transparent resinsheets of the laminate is preferably of a resin material that isthermally fusible to the article base material so that the photochromiclaminate is tightly integrated with the article base when produced withthe insert injection molding process. Thus, it is more preferred to havesame kind of material for both the article base and the transparentresin sheets.

Suitable sheet resin materials include polycarbonate, polysulfone,cellulose acetate butyrate (CAB), polyacrylates, polyesters,polystyrene, copolymer of an acrylate and styrene, blends of compatibletransparent polymers. Preferred resins are polycarbonate, CAB,polyacrylates, and copolymers of acrylate and styrene. Apolycarbonate-based resin is particularly preferred because of hightransparency, high tenacity, high thermal resistance, high refractiveindex, and most importantly, and especially its compatibility with thearticle base material when polycarbonate photochromic lenses aremanufactured with the photochromic polyurethane laminate of the presentinvention and the insert injection molding process. A typicalpolycarbonate based resin is polybisphenol-A carbonate. In addition,examples of the polycarbonate based resin include homopolycarbonate suchas 1,1′-dihydroxydiphenyl-phenylmethylmethane,1,1′-dihydroxydiphenyl-diphenylmethane,1,1′-dihydroxy-3,3′-dimethyldiphe-nyl-2,2-propane, their mutualcopolymer polycarbonate and copolymer polycarbonate with bisphenol-A.

While the thickness of a transparent resin sheet is not particularlyrestricted, it is typically 2 mm or less, and preferably 1 mm or lessbut not less than 0.025 mm.

Thermoplastic Polyurethane

As the thermoplastic polyurethane, it is preferably made from adiisocyanate, a polyol, and a chain extender. Thermoplasticpolyurethanes of this kind are known and may be obtained, for example,in accordance with U.S. Pat. Nos. 3,963,679 and 4,035,213, thedisclosures of which are incorporated herein by reference.

The thermoplastic polyurethane used in the present invention isparticularly prepared from a composition comprising a) an aliphaticisocyanate having a functionality of 2, b) at least one high molecularweight polyol having a nominal functionality of 2 and a molecular weightof from 500 to 6000 g/mole, preferably from 700 to 3000 g/mol, andcounting for from about 50% to about 98% by weight, preferably from 70%to 95%, of the total isocyanate reactive species in the composition, andc) at least one low molecular weight diol having a molecular weight offrom 62 to 499, and counting for from about 2% to about 50% by weight,preferably from 5% to 30%, of the total isocyanate reactive species inthe composition.

Polyols

The polyols of the present invention are those conventionally employedin the art for the preparation of polyurethane cast elastomers.Naturally, and often times advantageously, mixtures of such polyols arealso possible. Examples of the suitable polyols include polyetherpolyols, polyester polyols, polyurethane polyols, polybutadiene polyol,and polycarbonate polyols, while polyether and polyester types arepreferred.

Included among suitable polyether polyols are polyoxyethylene glycol,polyoxypropylene glycol, polyoxybutylene glycol, polytetramethyleneglycol, block copolymers, for example, combinations of polyoxypropyleneand polyoxyethylene glycols, poly-1,2-oxybutylene and polyoxyethyleneglycols, poly-1,4-tetramethylene and polyoxyethylene glycols, andcopolymer glycols prepared from blends or sequential addition of two ormore alkylene oxides. The polyalkylene polyether polyols may be preparedby any known process such as, for example, the process disclosed inEncyclopedia of Chemical Technology, Vol. 7, pp. 257-262, published byInterscience Publishers, Inc. (1951), the disclosure of which isincorporated herein by reference.

Polyethers which are preferred include the alkylene oxide additionproducts of polyhydric alcohols such as ethylene glycol, propyleneglycol, dipropylene glycol, trimethylene glycol, 1,2-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, hydroquinone,resorcinol glycerol, glycerine, 1,1,1-trimethylol-propane,1,1,1-trimethylolethane, pentaerythritol, 1,2,6-hexanetriol,.alpha.-methyl glucoside, sucrose, and sorbitol. Also included withinthe term “polyhydric alcohol” are compounds derived from phenol such as2,2-bis (4-hydroxyphenyl)-propane, commonly known as Bisphenol A.

The suitable polyester polyols include the ones which are prepared bypolymerizing ε-caprolactone using an initiator such as ethylene glycol,ethanolamine and the like. Further suitable examples are those preparedby esterification of polycarboxylic acids. Further suitable polyesterpolyols include reaction products of polyhydric, preferably dihydricalcohols to which trihydric alcohols may be added and polybasic,preferably dibasic carboxylic acids. Instead of these polycarboxylicacids, the corresponding carboxylic acid anhydrides or polycarboxylicacid esters of lower alcohols or mixtures thereof may be used forpreparing the polyesters. The polycarboxylic acids may be aliphatic,cycloaliphatic, aromatic and/or heterocyclic and they may besubstituted, e.g., by halogen atoms, and/or unsaturated. The followingare mentioned as examples: succinic acid; adipic acid; suberic acid;azelaic acid; sebacic acid; phthalic acid; isophthalic acid; trimelliticacid; phthalic acid anhydride; tetrahydrophthalic acid anhydride;hexahydrophthalic acid anhydride; tetrachlorophthalic acid anhydride,endomethylene tetrahydrophthalic acid anhydride; glutaric acidanhydride; maleic acid; maleic acid anhydride; fumaric acid; dimeric andtrimeric fatty acids such as oleic acid, which may be mixed withmonomeric fatty acids; dimethyl terephthalates and bis-glycolterephthalate. Suitable polyhydric alcohols include, e.g., ethyleneglycol; propylene glycol-(1,2) and -(1,3); butylene glycol-(1,4) and-(1,3); hexanediol-(1,6); octanediol-(1,8); neopentyl glycol;(1,4-bis-hydroxymethylcyclohexane); 2-methyl-1,3-propanediol;2,2,4-trimethyl-1,3-pentanediol; triethylene glycol; tetraethyleneglycol; polyethylene glycol; dipropylene glycol; polypropylene glycol;dibutylene glycol and polybutylene glycol, glycerine andtrimethlyolpropane. A preferred polyester polyol is polycaprolactonepolyol having an average molecular weight from 500 to 6,000, andpreferably from 700 to 3,000.

Diols

Suitable diols are those polyols listed above having a functionality of2 and a molecular weight of from 62 to 499. Preferred diols are1,4-butane-diol and 1,3-propane-diol.

Isocyanates

The diisocyanate component is preferably an aliphatic diisocyanate. Thealiphatic diisocyanate is selected from the group consisting of1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecamethylenediisocyanate, cyclohexane-1,3- and -1,4-diisocyanate,1-isocyanato-2-isocyanatomethyl cyclopentane,1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane (isophoronediisocyanate or IPDI), bis-(4-isocyanatocyclohexyl)-methane,2,4′-dicyclohexylmethane diisocyanate, 1,3- and1,4-bis-(isocyanatomethyl)-cyclohexane,bis-(4-isocyanato-3-methylcyclohexyl)-methane,.alpha.,.alpha.,.alpha.′,.alpha.′-tetramethyl-1,3- and/or -1,4-xylylenediisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethyl cyclohexane,2,4- and/or 2,6-hexahydrotoluylene diisocyanate, and mixtures thereof.Bis-(4-isocyanatocyclohexl)-methane is the preferred diisocyanate inoccurrence with the method of the present invention.

The polymerization process to make the thermoplastic polyurethane can becarried out in one-pot fashion, that is, all starting materials areinitially added into the reaction vessel. The polymerization process canalso be carried out with a prepolymer approach. That is, a polyurethaneprepolymer terminated with isocyanate groups is first obtained byreacting a stoichiometrically in excess diisocyanate with a polyol.Suitable equivalent ratio of diisocyanate to polyol in the presentinvention is from 1.2:1.0 to 8.0:1.0. A chain extender of diol is thenmixed with the prepolymer to complete the reaction. The NCO index of thethermoplastic polyurethane, formed from the quotient, which ismultiplied by 100, of the equivalent ratio of isocyanate groups to thesum of the hydroxyl groups of polyol and chain extender is within arange of 90 to 105, preferably between 92 and 101.

Catalysts such as organotin or other metallic soaps may be added in themixture to make a thermoplastic polyurethane. Example catalysts includedibutyltin dilaurate, stannous octoate, and cobalt naphthenate.

Isocyanate Prepolymer

The isocyanate prepolymer used in the photochromic polyurethanecomposition of the present invention is prepared in the same way as theprepolymer used to prepare the thermoplastic polyurethane in aprepolymer method described above. Preferably, the polyol and theisocyanate used to make the isocyanate prepolymer is the same as thepolyol to make the thermoplastic polyurethane. More preferably, theisocyanate is an aliphatic diisocyanate described in the previoussections, and the polyol is a polyester polyol having a molecular weightbetween 700 and 3,000. The molecular weight (number averaged) of theisocyanate prepolymer is preferably between 1,000 and 6,000, and morepreferably between 1,500 and 4,000. As an isocyanate group terminatedprepolymer, its NCO content is between 1.0% and 10.0%, preferablybetween 2.0% and 8.0%.

When mixing the isocyanate prepolymer and the thermoplastic polyurethanetogether, the mixing ratio by weight is in the range from 1:9 to 9:1,preferably from 1:3 to 3:1.

Photochromic Compounds

Suitable photochromic compounds in the context of the invention areorganic compounds that, in solution state, are activated (darken) whenexposed to a certain light energy (e.g., outdoor sunlight), and bleachto clear when the light energy is removed. They are selected from thegroup consisting essentially of benzopyrans, naphthopyrans,spirobenzopyrans, spironaphthopyrans, spirobenzoxzines,spironaphthoxazines, fulgides and fulgimides. Such photochromiccompounds have been reported which, for example, in U.S. Pat. Nos.5,658,502, 5,702,645, 5,840,926, 6,096,246, 6,113,812, and 6,296,785;and U.S. patent application Ser. No. 10/038,350, all commonly assignedto the same assignee as the present invention and all incorporatedherein by reference.

Among the photochromic compounds identified, naphthopyran derivativesare preferred for optical articles such as eyewear lenses. They exhibitgood quantum efficiency for coloring, a good sensitivity and saturatedoptical density, an acceptable bleach or fade rate, and most importantlygood fatigue behavior. These compounds are available to cover thevisible light spectrum from 400 nm to 700 nm. Thus, it is possible toobtain a desired blended color, such as neutral gray or brown, by mixingtwo or more photochromic compounds having complementary colors under anactivated state.

More preferred are naphtho[2,1b]pyrans and naphtho[1,2b]pyransrepresented by the following generic formula:

Substituents on various positions of the aromatic structure are used totune the compounds to have desired color and fading rate, and improvedfatigue behavior. For example, a photochromic dye may contain apolymerizable group such as a (meth)acryloyloxy group or a (meth)allylgroup, so that it can be chemically bonded to the host material throughpolymerization.

The quantity of photochromic compound(s) incorporated into thepolyurethane layer of the present invention is determined by the desiredlight blockage in the activated state and the thickness of thepolyurethane layer itself. The preferred outdoor visible lighttransmission of sunglasses is preferably between 5% and 50%, morepreferably between 8% and 30%, most preferably between 10% and 20%.Preferably, the amount of total photochromic substance incorporated intoor applied on the polyurethane layer may range from about 0.1 wt. % toabout 5 wt. % of the total polyurethane, and more preferably from about0.5 wt. % to about 3.0 wt. %. If the thickness of the polyurethane layeris 100 μm, between about 0.5 wt. % to about 1 wt. % of photochromiccompound(s) is needed to achieve an outdoor light transmission ofbetween 10% and 20%. The amount of photochromic compound(s) needed isinversely proportional to the thickness of the polyurethane layer. Inother words, to achieve the same outdoor light transmission the thickerthe polyurethane layer, the lower the concentration of photochromiccompound(s) needed. The concentration of the photochromic compound(s)also depends on the color intensity of the photochromic compound(s) atthe activated state.

Stabilizers

Additives such as antioxidants and light stabilizers are incorporatedinto the polyurethane layer in order to improve the fatigue resistanceof the photochromic compounds. Hindered amines are usually used as lightstabilizers, and hindered phenols are usually used as antioxidants.Preferred hindered amine light stabilizers include,bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacate, or a condensationproduct of 1,2,2,6,6-pentamethyl-4-piperidinol, tridodecyl alcohol and1,2,3,4-butanetetra caboxylic acid as tertiary hindered amine compounds.Preferred phenol antioxidants include,1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxy-phenyl)propionate]methane,and1,3,5-tris(3,5-di-t-butyl-4-hyroxybenzyl)-1,-3,5-triazine-2,4,6-(1H,3H,5H)-trione.Phenol antioxidants that contain 3 or more hindered phenols arepreferable.

Process to Make the Laminate

A photochromic laminate having a polyurethane layer in between twotransparent resin sheets in accordance with the present invention may beproduced through a variety of processes. Depending on the nature of thestarting material to the polyurethane, processes such ascasting-lamination (also referred to in the art as coating-lamination),and extrusion-lamination may be used.

To the photochromic polyurethane composition of the present invention, anovel casting-lamination process has been developed by the inventors.The process essentially comprises: a) preparing a solvent castingsolution by dissolving a solid thermoplastic polyurethane, at least oneisocyanate polyurethane prepolymer, at least one photochromic compound,and optional stabilizers in a proper solvent; b) cast the solution on arelease liner film; c) remove the solvent from the cast film to asubstantially dry state to form a photochromic polyurethane film; d)transfer-laminate the photochromic polyurethane film between twotransparent resin sheets; e) cure the photochromic polyurethane film,thereby forming a photochromic polyurethane laminate.

To cast a photochromic polyurethane film, a thermoplastic polyurethane,an isocyanate prepolymer, selected photochromic compounds and othernecessary additives are first dissolved in a suitable solvent or in amix of solvents to form a cast solution. The solid concentration in sucha solution is usually 15% to 50%, by weight, and the solution has aviscosity suitable for coating. For example, suitable viscosity of thecast solution for using a slot die method is within the range from 500cPs to 5000 cPs. Examples of suitable solvents that may be used todissolve polyurethanes include cyclohexane, toluene, xylene and ethylbenzene, esters such as ethyl acetate, methyl acetate, isopropylacetate, n-propyl acetate, isobutyl acetate, n-butyl acetate, isoamylacetate, methyl propionate and isobutyl propionate, ketones such asacetone, methylethyl ketone, diethyl ketone, methylisobutyl ketone,acetyl acetone and cyclohexyl ketone, ether esters such as cellosolveaetate, diethylglycol diaetate, ethyleneglycol mono n-butyletheracetate, propylene glycol and monomethylether acetate, tertiary alcoholssuch as diacetone alcohol and t-amyl alcohol and tetrahydrofuran. Ethylacetate, methyl ethyl ketone, cyclohexane, tetrahydrofuran, toluene andcombinations thereof are preferable.

The solution is then cast on a release liner by using a method known tothose skilled in the art, such as slot-die, knife-over-roll,reverse-roll, gravure, etc. Slot die and knife-over-film are referred.Slot die method is especially preferred due to its capability to handlewide range of solution viscosity and to cast uniform films. A releaseliner may consist of a base film and a release coating or simply a filmitself. Films with surface energy low enough to provide easy release ofthe cast film can be used by itself. Examples include low energypolyolefins and fluoropolymers. Most commercially available releaseliners are based on polyester film coated with a release coating. Therelease coating has a proper surface energy so that a cast solution orcoating forms a uniform film (e.g., without beading) on it. At the sametime the release coating does not provide good adhesion to the driedfilm so that the film can be easily peeled off. Release coatings includesilicone (siloxane) based and non-silicone base such as fluoropolymers.A liner based on polyester (PET) with cured siloxane release coating ispreferred due to the dimensional stability, flatness, handling, solventresistance, low cost. Suitable liners should have a thickness of from 25micrometers to 130 micrometers.

The wet photochromic polyurethane film cast on the release liner issequentially dried in a forced air oven system. The solvent will besubstantially evaporated so that the solvent retention in thephotochromic polyurethane film is low enough to not cause any defects(e.g., bubbling) in the future laminate. The solvent retentionpreferably is less than 2 wt. %, more preferably less than 1 wt. %, andmost preferably less than 0.5 wt. %. Conventional methods such as hotair dryers may be used to evaporate the solvent before lamination. Thedrying conditions, such as temperature and air flow rate in the oven,for a desired solvent retention value depends on the nature of thesolvent, the thickness of the cast film, the type of the release liner,and the web speed. The drying conditions should not be so aggressive tocause any surface defects in the cast film. Example defects are blisters(bubbles) and orange peel. Preferably, the drying oven system hasmulti-zones whose drying conditions are controlled separately.

The thickness of the dried photochromic polyurethane layer is from about5 micrometers to about 150 micrometers. For using the photochromiclaminate in an insert injection molding process to make plasticphotochromic lenses, the thickness of the photochromic polyurethane ispreferably between 5 micrometers and 80 micrometers. The thicknessvariation of the photochromic polyurethane layer should be controlled inorder to produce a uniform light blockage at the activated state. Athickness variation of less than 15% over the width of the laminate isrequired and preferably less than 10% and more preferably less than 5%.

The transfer-lamination of the dried photochromic polyurethane film totwo transparent resin sheets to form a laminate of the polyurethane filmbetween the two resin sheets, may be done by either a sequentiallamination process or an in-line lamination process. In a sequentiallamination process, the dried polyurethane film on the release liner isfirst laminated to the first transparent resin sheet through a firstlamination station. The semi-laminate consisting of the release liner,the polyurethane film, and the resin sheet, is then wound up on a core.The wind is then brought to a second lamination station where therelease liner is peeled off and the second transparent sheet islaminated to the polyurethane film to form the final photochromicpolyurethane laminate. The first and the second lamination stations maybe the same one. The lamination may be conducted between two chromecoated steel rolls or between one steel roll and one rubber roll,although the later is preferred.

According to the findings of the inventors, an in-line laminationprocess is more preferred. In such a process, the second transparentresin sheet is immediately laminated to the semi-laminate without firstwinding the semi-laminate. The in-line lamination may be done with twotwo-roll lamination stations, or more conveniently be conducted on onethree-roll setup in which the first roll and the second roll form afirst nip, and the second roll and the third roll form a second nip. Thedried polyurethane film on the release liner is first laminated to thefirst transparent resin sheet through the first nip. Without forming andwinding a semi-laminate, the release liner is peeled off, and the secondtransparent resin sheet is immediately laminated to the exposed side ofthe polyurethane film on the first transparent resin sheet, through thesecond nip. This in-line lamination process will significantly increasethe productivity. It also eliminates an extra winding step and reducesthe possibilities of defects in the polyurethane film associated withthe winding step. Example defects are de-lamination between thepolyurethane film and the transparent resin sheet, impressions in thepolyurethane film caused by possible external particles under windingpressure.

The photochromic polyurethane laminate thus formed according to thepresent invention needs to be cured before application. The curing ispreferably carried in two stages: a) ambient curing for 1 day to 1 week,b) post curing at elevated temperature of from 50° C. to 130° C. for 8hours to 1 week.

If the solvent selected to dissolve the photochromic polyurethanecomposition does not whiten the transparent resin sheet, a direct caston the resin sheet may be employed. In this case, a simple two-rolllamination setup is acceptable for making a photochromic polyurethanelaminate.

In an alternative process, the photochromic layer from a thermoplasticpolyurethane and isocyanate-terminated polyurethane prepolymer may beco-extruded utilizing a single- or twin-screw extruder. The extrudedphotochromic polyurethane film will then be immediately hot-laminatedbetween two transparent resin sheets to form the photochromicpolyurethane laminate. The photochromic compounds and other additivesmay be incorporated into the polyurethane during the resin synthesisstage or melt-mixed prior to extrusion.

Although the photochromic laminate according to the present invention isespecially suitable for making photochromic polycarbonate lenses throughthe insert injection molding process described in commonly assigned U.S.Pat. No. 6,328,446, it can also be used as-is for other photochromictransparencies such as goggles and face shields. The photochromiclaminate may also be incorporated into other types of eyewear lensessuch as cast resin lenses with a process described in U.S. Pat. No.5,286,419.

The photochromic polyurethane laminate in accordance with the presentinvention will now be illustrated with reference to the followingexamples, which are not to be construed as a limitation upon the scopeof the invention in any way.

In the examples, all values are expressions of weight %. CR49 and CR59are tradenames of photochromic dyes available from Corning Corp.Grey-762 is proprietary grey photochromic dye. Irganox-1010 as anantioxidant, Tinuvin-144 and Tinuvin-765 as light stabilizers areavailable from CIBA (Tarrytown, N.Y., US).

To visually evaluate the activation and the photochromic polyurethanelayer uniformity, a photochromic laminate or lens was exposed to UVirradiation (12 mw/m2) for 5 minutes.

Example 1

Preparation of Isocyanate Polyurethane Prepolymer A: In a 3-necked flaskequipped with an overhead stirrer, thermocouple, and a vacuum adapter,393.5 g (3 equivalents) of 4,4′-dicyclohexylmethanediisocyanate (H12MDI,available from Bayer as Desmodur W) was charged into the reactor andstirred at ambient temperature. 1000 g (2 equivalents) of apolycaprolactone diol having an OH number of 112 mg KOH/g and a numberaverage molecular weight of about 1000 g/mole (available from DowChemical as Tone™ 2221) was preheated in an oven to 80° C. and added tothe reactor. The mixture was allowed to stir for about 15 minutes,before adding 6 g of dibutyltin dilaurate catalyst (available from AirProducts as T-12). The reaction flask was evacuated (<0.1 mm HG) andheld at 90° C. for 6 hours. An aliquot of the prepolymer was withdrawnand titrated for isocyanate content using standard n-butyl aminetitration. The isocyanate content was found to be 2.92% (theory; 3.0%).

Example 2

Preparation of Isocyanate Polyurethane Prepolymer B: In a 3-necked flaskequipped with an overhead stirrer, thermocouple, and a vacuum adapter,613.0 g (4.67 equivalents) of 4,4′-dicyclohexylmethanediisocyanate(H12MDI, available from Bayer as Desmodur W) was charged into thereactor and stirred at ambient temperature. 1000 g (2 equivalents) of apolycaprolactone diol having an OH number of 112 mg KOH/g and a numberaverage molecular weight of about 1000 g/mole (available from DowChemical as Tone™ 2221) was preheated in an oven to 80° C. and added tothe reactor. The mixture was allowed to stir for about 15 minutes,before adding 8 g of dibutyltin dilaurate catalyst (available from AirProducts as T-12). The reaction flask was evacuated (<0.1 mm HG) andheld at 90° C. for 6 hours. An aliquot of the prepolymer was withdrawnand titrated for isocyanate content using standard n-butyl aminetitration. The isocyanate content was found to be 6.75% (theory; 7.0%).

Example 3

Preparation of Thermoplastic Polyurethane: A thermoplastic polyurethanehaving a theoretical NCO index of 95 was prepared as following. Theisocyanate prepolymer B (927.2 g) prepared in Example 2 was heated invacuo (<0.1 mm HG) with stirring to 80° C. and 1,4-butane-diol (72.8 g)as the chain extender and 3 g of dibutyltin dilaurate catalyst werecombined with the prepolymer while keeping stirring. The mixture wasstirred for 30 seconds and subsequently poured into a Teflon lined tray.The tray containing the casting was cured in an oven at 85° C. for 24hours.

Example 4

A solution was first made by dissolving 4 g of the thermoplasticpolyurethane prepared in Example 3 in 16 g of anhydrous tetrahydrofuran.To the solution was further added 4 g of the isocyanate prepolymerprepared in Example 1, 0.14 g of CR49 dye, 0.02 g CR59 dye, 0.17 g eachof Irganox-1010, Tinuvin-144, and Tinuvin-765. The mixture was stirredat room temperature for 3 hours before cast on an easy release liner(available from CPFilms as T-50) with draw bar targeting a 38 micrometerdry film thickness. The solvent in the cast film was evaporated at 60°C. for 5 minutes with airflow above the film. The dried film wastransfer-laminated between two 0.3 mm thick polycarbonate sheets(available from Teijin as PC-1151) with a bench top roller laminator.After 4 days under ambient, the laminate was cured at 70° C. for 3 days.

The laminate was cut into a 76 mm disc and used to make a segmentedmulti-focal polycarbonate photochromic lens. After the insert injectionmolding process with common molding parameters, the finished lens had anacceptable thin, crisp segment line. No polyurethane bleeding from thelaminate was observed. The lens showed quick and uniform photochromicactivation. No any lamination defects were observed.

Example 5

A solution having 28.2% solid, was first prepared by dissolving 1950 gof the thermoplastic polyurethane prepared as in Example 3 in 7550 g ofanhydrous tetrahydrofuran. To the solution was further added 780 g ofthe isocyanate prepolymer prepared as in Example 1, 59 g each of “762”dye, Irganox-1010, Tinuvin-144, and Tinuvin-765. The mixture was stirredat room temperature for 3 hours then set overnight before cast on aneasy release liner (available from Saint-Gobain as 8310) at a web speedof 5.5 feet per minute in a pilot coater equipped with a slot die, atwo-zone drying oven, and a three-roll lamination station. The solventin the cast film was evaporated at 70° C. for 1 minute and 120° C. foranother minute with forced airflow above the film. The dried film was 38micrometer thick and had a solvent retention of 0.1%. It wastransfer-laminated between two 0.3 mm thick polycarbonate sheets(available from Teijin as PC-1151) with an in-line process (withoutwinding the semi-laminate of the release liner, polyurethane film, andthe first polycarbonate sheet). After 4 days in ambient (22° C. and35%˜50% RH), the laminate was cured at 70° C. for 3 days.

The laminate was cut into 76 mm discs and used to make a segmentedmulti-focal polycarbonate photochromic lenses. After the insertinjection molding process with common molding parameters, the finishedlens had an acceptable thin, crisp segment line. No polyurethanebleeding from the laminate was observed. The lens showed quick anduniform photochromic activation. No any lamination defects wereobserved.

Example 6

A solution having 35.3% solid, was first prepared by dissolving 1950 gof the thermoplastic polyurethane prepared as in Example 3 in 7742 g ofanhydrous tetrahydrofuran. To the solution was further added 1950 g ofthe isocyanate prepolymer prepared as in Example 1, 68 g of CR49 dye, 10g CR59 dye, 85 g each of Irganox-1010, Tinuvin-144, and Tinuvin-765. Themixture was stirred at room temperature for 3 hours then set overnight,then cast directly on a first 0.3 mm thick polycarbonate sheet(available from Teijin as PC1151) at a web speed of 5.5 feet per minutein a pilot coater equipped with a slot die, a two-zone drying oven, anda three-roll lamination station. The solvent in the cast film wasevaporated at 94° C. for 1 minute and 127° C. for another minute withforced airflow above the film. The dried film was 25 micrometer thickand had a solvent retention of 0.1%. A second 0.3 mm thick polycarbonatesheet was laminated on the exposed side of the dried polyurethane filmon the first polycarbonate sheet. After 4 days in ambient (22° C. and35%˜50% RH), the laminate was cured at 70° C. for 3 days. The laminateobtained was clear. No solvent whitening on the polycarbonate sheets wasseen.

Comparison Example 1

To 10 g of Hysol® (Loctite) U-10FL urethane adhesive resin are dissolved1.5% of “762” dye, 2.0% of Tinuvin 144, and 2.0% of Tinuvin 765. Then,9.1 g of Hysol® U-10FL urethane adhesive hardener is mixed in to form aliquid adhesive.

The adhesive was coated with a draw bar directly on a polycarbonatesheet (0.3 mm thick, available from Teijin as 1151) to form a 38micrometer cast film. Another polycarbonate sheet was laminated onto theadhesive through a bench top roller laminator. Some adhesive wassqueezed out. The laminate was allowed to cure at room temperatureovernight, then is post cured at 65° C. for 10 hours.

When the photochromic laminate was activated, thin spots (lightlyactivated due to thinner spots in the polyurethane layer) andnon-uniformity of activation due to thickness gradient across thelaminate were observed.

Comparison Example 2

Example 4 was followed, except the isocyanate prepolymer was neglected.The photochromic polyurethane layer was 38 micrometers thick. Thelaminate showed uniform photochromic activation. No lamination defectswere observed. However, when molded into a polycarbonate lens as inExample 4, severe polyurethane bleeding was observed at the edge of thelaminate.

The foregoing detailed description of the preferred embodiments of theinvention has been provided for the purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise embodiments disclosed. Many modifications andvariations will be apparent to practitioners skilled in the art to whichthis invention pertains. The embodiments were chosen and described inorder to best explain the principles of the invention and its practicalapplication, thereby enabling others skilled in the art to understandthe invention for various embodiments and with various modifications asare suited to the particular use contemplated. It is intended that thescope of the invention be defined by the following claims and theirequivalents.

Although the invention has been described in terms of particularembodiments and applications, one of ordinary skill in the art, in lightof this teaching, can generate additional embodiments and modificationswithout departing from the spirit of or exceeding the scope of theclaimed invention. Accordingly, it is to be understood that the drawingsand descriptions herein are proffered by way of example to facilitatecomprehension of the invention and should not be construed to limit thescope thereof.

What is claimed is:
 1. A method of making a photochromic lenscomprising: providing a photochromic layer having a front side and arear side; providing a cast lens mold; placing said photochromic layerinto said cast lens mold; injecting a resin into said cast lens moldagainst said front side of said photochromic layer; injecting a resininto said cast lens mold against said rear side of said photochromiclayer; and, curing said resin.
 2. A method according to claim 1 whereinproviding a photochromic layer comprises preparing a photochromiclaminate film.
 3. A method according to claim 2 wherein preparing aphotochromic laminate film comprises laminating at least one protectivelayer against a cast photochromic layer.
 4. A method according to claim1 wherein curing said resin comprises UV curing of said resin.
 5. Amethod according to claim 1 wherein curing said resin comprises thermalcuring of said resin.
 6. A method according to claim 1 furthercomprising forming said photochromic layer prior to placing saidphotochromic layer into said cast lens mold.
 7. A method of making acast photochromic lens comprising: providing a lens mold; providing aphotochromic film; inserting said photochromic film into said mold suchthat a space is present at least between a front surface of said moldand said photochromic film; introducing a curable resin into said moldand thereby filling said space with said curable resin; and, curing saidresin.
 8. A method according to claim 7 wherein providing a photochromicfilm comprises providing a thermoplastic polyurethane photochromic film.9. A method according to claim 8 wherein said providing a thermoplasticpolyurethane photochromic film includes providing a polyurethanephotochromic film having a resin layer on either side of saidpolyurethane photochromic film.
 10. A method according to claim 7wherein curing said resin comprises one of UV curing and thermal curing.11. A method according to claim 7 wherein the providing of saidphotochromic film includes forming said photochromic film tosubstantially confirm to a base curve of said mold.
 12. A methodaccording to claim 7 wherein the providing of said photochromic filmincludes preparing a cast photochromic film.
 13. A cast lens comprising:a photochromic film; cast resin encapsulating said photochromic film;said resin having been cured by heat or radiation